Integrated Ocean Drilling Program (IODP) Expedition 339, Mediterranean Outflow, was executed from November 2011 to January 2012 on board the research vessel JOIDES Resolution. The expedition, carrying an international team of 35 scientists from 14 countries, recovered five kilometers of core samples from an area never before drilled along the Gulf of Cadiz and west off Portugal. The scientific party found new evidence of a deep-earth tectonic pulse, retrieved a detailed record of climate changes, and made key discoveries that could influence the future of oil and gas exploration.

The Strait of Gibraltar is one of the most important oceanic gateways, which re-opened less than 6 million years ago after being isolated from the Atlantic for several hundred millennia. Today, deep below the sea surface, a powerful cascade of Mediterranean water spills out through the Strait of Gibraltar into the Atlantic Ocean. Because this water is saltier than the Atlantic, and therefore heavier, it plunges more than 1000 meters downslope, scouring the rocky seafloor, carving deep-sea canyons, and building up mountains of mud on a little known submarine landscape.

These sediments, called contourites because the currents that deposit them closely follow the contours of the ocean basin, hold a record of climate change and tectonic activity that spans much of the past 5.3 million years, says Dorrik Stow, Co-Chief Scientist for Expedition 339, from Heriot-Watt University in the UK. “The expedition brought us many of the eagerly anticipated answers to our questions, as well as wholly unexpected scientific results.”